The present invention relates to methods, compounds, compositions and kits useful for delivering to a target site a targeting moiety that is conjugated to one member of a ligand/anti-ligand pair. After localization and clearance of the targeting moiety conjugate, direct or indirect binding of a diagnostic or therapeutic agent conjugate at the target site occurs. Methods for radiometal labeling of biotin and for improved radiohalogenation of biotin, as well as the related compounds, are also disclosed. Also, clearing agents, anti-ligand-targeting moiety conjugates, target cell retention enhancing moieties and additional methods are set forth.
Conventional cancer therapy is plagued by two problems. The generally attainable targeting ratio (ratio of administered dose localizing to tumor versus administered dose circulating in blood or ratio of administered dose localizing to tumor versus administered dose migrating to bone marrow) is low. Also, the absolute dose of radiation or therapeutic agent delivered to the tumor is insufficient in many cases to elicit a significant tumor response. Improvement in targeting ratio or absolute dose to tumor is sought.
The present invention is directed to diagnostic and therapeutic pretargeting methods, moieties useful therein and methods of making those moieties. Such pretargeting methods are characterized by an improved targeting ratio or increased absolute dose to the target cell sites in comparison to conventional cancer therapy.
The present invention describes chelate-biotin compounds and radiohalogenated biotin compounds useful in diagnostic and therapeutic pretargeting methods. The present invention also provides targeting moiety-ligand, such as biotin, compounds useful in diagnostic and therapeutic pretargeting methods. Selection of moieties and methodologies used to enhance internalization (of chemotherapeutic drugs, for example) or to enhance retention at the target cell surface (of radionuclides, for example) is also discussed.
In addition, the present invention provides targeting moiety-anti-ligand, such as avidin or streptavidin, compounds useful in diagnostic and therapeutic pretargeting methods. Other ligand-anti-ligand systems including the zinc finger protein-dsDNA fragment binding pair are also contemplated. Preparation and purification of such anti-ligand-targeting moiety compounds are also discussed.
The present invention also provides clearing agents to facilitate the removal of circulating targeting moiety-ligand (two-step) or targeting moiety-anti-ligand (two-step) or anti-ligand (three-step) from the mammalian recipient. Preferred clearing agents are classifiable as galactose-based and non-galactose-based. Within each category, preferable clearing agents are polymeric or protein based. Particulate agents, extracorporeal procedures and in vivo devices are also contemplated for use in the practice of the present invention.
Also, the present invention is directed to methods using streptavidin as an anti-ligand to enhance retention of radionuclide at target cell sites, with pretargeting protocols constituting one such method. More specifically, these embodiments of the present invention involve either (1) targeting moiety-streptavidin-radionuclide (with the radionuclide bound to streptavidin directly or through a chelate or linker), as well as (2) targeting moiety-biotin administered prior to streptavidin-radionuclide, or (3) biotin-radionuclide bound to a pretargeted streptavidin containing molecule.
The present invention further provides pretargeting methods employing intraarterial or other local administration of the therapeutic moiety-containing molecule to achieve greater localization thereof to artery-supplied target cell populations. Other methods of the present invention involve administration of short duration bone marrow protecting agents or vascular permeability enhancing agents prior to radionuclide-ligand molecule or radionuclide-anti-ligand molecule administration. Further, monovalent targeting moieties, such as Fv or Fab antibody fragments, are useful in the inventive pretargeting methods. Delivery of other, non-radioactive therapeutic agents, such as chemotherapeutic drugs, anti-tumor agents (e.g., cytokines) and toxins, to target cells using the pretargeting methods of the present invention is also described.